Multi-orbital Kondo screening in strongly correlated polyradical nanographenes

TL;DR

This paper investigates the coexistence of Kondo and spin excitation signals in polyradical nanographenes, revealing multi-orbital Kondo screening mechanisms through theoretical modeling and numerical calculations.

Contribution

It introduces a perturbative model to identify antiferromagnetic channels responsible for Kondo screening in strongly correlated nanographenes.

Findings

Kondo signals are explained by multi-orbital screening.

Numerical renormalization group confirms the Kondo regime.

The framework applies to similar strongly correlated systems.

Abstract

We discuss coexistence of Kondo and spin excitation signals in tunneling spectroscopy in strongly correlated polyradical $\pi$-magnetic nanographenes on a metal surface. The Kondo signal is rationalized by a multi-orbital Kondo screening of the unpaired electrons. The fundamental processes are spin-flips of antiferromagnetic (AFM) order involving charged molecular multiplets. We introduce a~perturbative model, which provides simple rules to identify the presence of AFM channels responsible for Kondo screening. The Kondo regime is confirmed by numerical renormalization group calculations. This framework can be applied to similar strongly correlated open-shell systems.